Lightning imaging method based on piezoelectric array waveguide response

Abstract

The application discloses a lightning stroke imaging method based on piezoelectric array waveguide response, comprising the following steps: S1, arranging a sparse piezoelectric-waveguide array in a measured structure; S2, acquiring a lightning stroke waveguide response signal of the sparse piezoelectric-waveguide array; S3, filtering and processing the lightning stroke waveguide response signal through convolution of a sinusoidal modulation signal; and S4, pre-processing the lightning stroke waveguide response signal and implementing lightning stroke comprehensive imaging based on signal delay superposition. The lightning stroke imaging method based on piezoelectric array waveguide response is adopted, the lightning stroke waveguide response signal of the piezoelectric array is subjected to delay superposition for comprehensive imaging, online positioning monitoring of lightning stroke points is realized, and therefore high-precision imaging of lightning stroke events of large-area aviation composite material structures can be realized.

Description

Technical Field

[0001] This invention relates to the field of aerospace structural health monitoring technology, and in particular to a lightning strike imaging method based on the piezoelectric array guided wave response. Background Technology

[0002] Aerospace composite structures are inevitably threatened by lightning strikes during their service life. Compared to traditional metallic materials, aerospace composites have higher specific strength but lower electrical conductivity, making them more susceptible to severe structural damage from lightning strikes. To ensure the safety of modern composite aircraft in lightning environments, the need for online monitoring of lightning strike events on aerospace composite structures is becoming increasingly urgent. However, due to the short duration, high energy, and complex and harsh electromagnetic field environment of lightning strikes, effective technical methods for real-time online monitoring of lightning strike events still lack.

[0003] Currently, in the field of lightning strike monitoring of composite materials, researchers have been striving to achieve online monitoring of aircraft for important parameters of the direct effects of lightning strikes, such as severity and location (i.e., the lightning strike attachment point). Research on the severity of the direct effects of lightning strikes is mainly divided into two aspects: thermal effects and impact force effects. The former mainly relies on instruments such as high-speed cameras, infrared thermal imagers, and fiber optic temperature probes for observation. These techniques require complex specialized equipment and are generally only used for basic lightning strike observations in laboratories, making it difficult to achieve online aircraft monitoring. The latter mainly relies on FBG sensors to measure the strain of composite materials under lightning impact force or using piezoelectric thin-film pressure sensors to sense the magnitude of the lightning impact force load. However, these methods are essentially in-situ monitoring methods and cannot be applied to online aircraft lightning strike monitoring scenarios where the actual attachment point is unknown.

[0004] Research on aircraft online monitoring of lightning strike locations (i.e., lightning strike attachment points) mainly includes two methods: the all-fiber lightning current monitoring method based on the Faraday magneto-optical effect and the window-induction lightning current monitoring method. The former has developed corresponding sensors and airborne measurement modules and successfully conducted flight tests. However, the monitoring principle of this method requires the fiber optic sensing loop used to sense the lightning current to be arranged around the entire outer surface of the fuselage, which seriously restricts its practical application. The latter uses the magneto-electric induction effect to measure the physical quantity of the magnetic field that penetrates the window during a lightning strike to achieve aircraft lightning current monitoring. However, this method relies on a relatively complex measurement system and cannot achieve precise positioning of the lightning strike attachment point. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a lightning strike imaging method based on piezoelectric array guided wave response. By superimposing the delayed signals of the piezoelectric array lightning strike guided wave response, a comprehensive imaging method is achieved, enabling online location monitoring of the lightning strike point. This allows for high-precision imaging of large-area lightning strike events on aerospace composite material structures.

[0006] To achieve the above objectives, the present invention provides a lightning strike imaging method based on the piezoelectric array guided wave response, comprising the following steps:

[0007] S1. Arrange a sparse piezoelectric-guided wave array in the structure under test;

[0008] S2. Obtain the lightning-guided wave response signal of the sparse piezoelectric-guided wave array;

[0009] S3. The lightning guided wave response signal is filtered by convolutional sinusoidal modulation signal;

[0010] S4. Lightning guided wave response signal preprocessing and implementation of lightning strike integrated imaging based on signal delay superposition.

[0011] Preferably, in step S1, N piezoelectric elements are arranged on the structure under test to form a sparse piezoelectric-waveguide array, where N≥3.

[0012] Preferably, in step S2, when a lightning strike occurs, the individual piezoelectric elements P in the sparse piezoelectric-guided wave array are passively acquired. i Lightning-guided wave response signal s i (t), where t is a time variable, i = 1, 2, ..., N.

[0013] Preferably, in step S3, the convolutional sinusoidal modulation signal is combined with the lightning-guided wave response signal s i (t) is convolved to obtain a narrowband lightning guided wave response signal with more concentrated energy.

[0014] Preferably, step S3 specifically includes the following steps:

[0015] S31, Response signals s for each lightning strike guided wave i (t) Perform low-pass filtering to remove high-frequency noise;

[0016] S32, For each lightning strike guided wave response signal s after filtering out high-frequency noise. i (t) Perform time-frequency domain analysis to determine the main guided wave modes in the signal, as well as the frequency range of the signal components and main distribution of the guided wave modes;

[0017] S33. Determine the narrowband excitation signal v based on the frequency range determined in step S32. a (t);

[0018] S34, v a (t) and the lightning-guided wave response signals of each structure s i (t) is convolved to obtain the structural narrowband lightning-guided wave response signal v. i (t).

[0019] Preferably, the preprocessing of the lightning guided wave response signal in step S4 is as follows: determining each lightning guided wave response signal s based on the crosstalk location. i (t) reference time t off .

[0020] Preferably, the implementation of lightning strike comprehensive imaging based on signal delay superposition in step S4 is as follows: using the individual lightning guided wave response signals s i (t) reference time t off Using these signals as the starting points, and performing delayed superposition and comprehensive imaging processing, the comprehensive imaging results of the lightning strike are obtained.

[0021] Preferably, the delay-overlay composite imaging processing described in step S4 specifically includes the following steps:

[0022] S41, using each lightning strike guided wave response signal s i (t) reference time t off Using the starting point of each signal, the guided wave response from point o to point P is calculated according to the following formula. i Propagation time t oi (x,y) is:

[0023]

[0024] Among them, (x i ,y i ) is a piezoelectric element P i The coordinates, c io For the guided wave response of a lightning strike to propagate from point O to P i wave speed;

[0025] S42, convert each lightning strike guided wave response signal s i (t) The magnitudes of the values ​​at point o are summed to calculate the pixel value of point o:

[0026]

[0027] Therefore, the present invention has the following beneficial effects:

[0028] (1) Online monitoring and location of lightning strikes on large-area aerospace composite material structures were achieved by using a sparse piezoelectric-guided wave array;

[0029] (2) The reference time of the lightning guided wave response signal was determined by crosstalk, which solved the problem that the pre-acquisition time of the lightning guided wave response signal was unknown and it was difficult to directly implement delayed superposition imaging. Therefore, it can be used for large-area high-precision imaging of actual aerospace composite material structures struck by lightning.

[0030] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0031] Figure 1 This is a flowchart of a lightning strike imaging method based on the piezoelectric array guided wave response according to the present invention;

[0032] Figure 2 This diagram illustrates the distribution of the piezoelectric element and lightning source in the carbon fiber plate in an experimental example of the present invention.

[0033] Figure 3 The diagram shows the shock response guided wave signal s3(t) obtained by the piezoelectric element P3 in the experimental example of the present invention.

[0034] Figure 4 The diagram shows the shock response guided wave signal s4(t) obtained from the piezoelectric element P4 in the experimental example of the present invention.

[0035] Figure 5 The narrowband excitation signal v with a center frequency of 25 kHz is used in the experimental example of this invention. a (t) Results plot;

[0036] Figure 6 The diagram shows the results of a narrowband impulse guided wave signal v3(t) with a center frequency of 25kHz obtained by the piezoelectric element P3 in the experimental example of the present invention.

[0037] Figure 7 The diagram shows the results of a narrowband shock wave signal v4(t) with a center frequency of 25kHz obtained by the piezoelectric element P4 in the experimental example of the present invention.

[0038] Figure 8 This is a lightning strike imaging result of an experimental example of the present invention. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings. It should be noted that this embodiment is based on the present technical solution and provides detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to this embodiment.

[0040] It should be noted that delay superposition is a simple and effective large-area imaging method for sparse piezoelectric-guided wave arrays. Similar to the guided wave response generated by external impact on composite material structures, the lightning guided wave response includes lightning event information, including the spatial location of the lightning strike attachment point. Therefore, the delay superposition piezoelectric array guided wave imaging method can be used to realize online monitoring of the location of the lightning strike attachment point on composite material structures.

[0041] Figure 1 This is a flowchart of a lightning strike imaging method based on the piezoelectric array guided wave response according to the present invention, as shown below. Figure 1 As shown, a lightning strike imaging method based on piezoelectric array guided wave response includes the following steps:

[0042] S1. Arrange a sparse piezoelectric-guided wave array in the structure under test;

[0043] Preferably, in step S1, N piezoelectric elements are arranged on the structure under test to form a sparse piezoelectric-waveguide array, where N≥3.

[0044] S2. Obtain the lightning-guided wave response signal of the sparse piezoelectric-guided wave array;

[0045] Preferably, in step S2, when a lightning strike occurs, the individual piezoelectric elements P in the sparse piezoelectric-guided wave array are passively acquired. i Lightning-guided wave response signal s i (t), where t is a time variable, i = 1, 2, ..., N.

[0046] S3. The lightning guided wave response signal is filtered by convolutional sinusoidal modulation signal;

[0047] Preferably, in step S3, the convolutional sinusoidal modulation signal is combined with the lightning-guided wave response signal s i (t) is convolved to obtain a narrowband lightning guided wave response signal with more concentrated energy.

[0048] Preferably, step S3 specifically includes the following steps:

[0049] S31, Response signals s for each lightning strike guided wave i (t) Perform low-pass filtering to remove high-frequency noise;

[0050] S32, For each lightning strike guided wave response signal s after filtering out high-frequency noise. i (t) Perform time-frequency domain analysis to determine the main guided wave modes in the signal, as well as the frequency range of the signal components and main distribution of the guided wave modes;

[0051] S33. Determine the narrowband excitation signal v based on the frequency range determined in step S32. a (t);

[0052] S34, v a (t) and the lightning-guided wave response signals of each structure s i (t) is convolved to obtain the structural narrowband lightning-guided wave response signal v. i (t).

[0053] S4. Lightning guided wave response signal preprocessing and implementation of lightning strike integrated imaging based on signal delay superposition.

[0054] Preferably, the preprocessing of the lightning guided wave response signal in step S4 is as follows: determining each lightning guided wave response signal s based on the crosstalk location. i (t) reference time t off .

[0055] Preferably, the implementation of lightning strike comprehensive imaging based on signal delay superposition in step S4 is as follows: using the individual lightning guided wave response signals s i (t) reference time t off Using these signals as the starting points, and performing delayed superposition and comprehensive imaging processing, the comprehensive imaging results of the lightning strike are obtained.

[0056] Preferably, the delay-overlay composite imaging processing described in step S4 specifically includes the following steps:

[0057] S41, using each lightning strike guided wave response signal s i (t) reference time t off Using the starting point of each signal, the guided wave response from point o to point P is calculated according to the following formula. i Propagation time t oi (x,y) is:

[0058]

[0059] Among them, (x i ,y i ) is a piezoelectric element P i The coordinates, c io For the guided wave response of a lightning strike to propagate from point O to P i wave speed;

[0060] S42, convert each lightning strike guided wave response signal s i (t) The magnitudes of the values ​​at point o are summed to calculate the pixel value of point o:

[0061]

[0062] Experimental Example

[0063] This embodiment uses a carbon fiber composite laminate structure with a layup direction of [0° / 45° / -45° / 90°]s as the test structure, with dimensions of 600mm × 600mm × 2mm. Four piezoelectric elements P1 to P4 are arranged in the structure to form a monitoring array. A coordinate system is established with the center of the structure as the origin. Figure 2 The rectangular coordinate system shown in Table 1 illustrates the distribution of the lightning source E1 and the piezoelectric element within the coordinate system.

[0064] Table 1 shows the coordinates of the piezoelectric element and the impact source.

[0065] Coordinates (mm, mm) Coordinates (mm, mm) <![CDATA[P1]]> (200，200) <![CDATA[P3]]> (-200，-200) <![CDATA[P2]]> (-200，200) <![CDATA[P4]]> (200，-200) <![CDATA[E1]]> (-31，24)

[0066] This embodiment of a method for imaging lightning strikes on composite material structures based on piezoelectric-guided wave arrays includes the following steps:

[0067] (1) Arrange a sparse piezoelectric-waveguide array in the structure under test:

[0068] For carbon fiber composite laminate structures, according to Figure 2 A sparse piezoelectric waveguide array consisting of four piezoelectric elements is arranged.

[0069] (2) Obtaining the lightning-guided wave response signal of the sparse piezoelectric-guided wave array:

[0070] When a lightning strike occurs, the passive acquisition of individual piezoelectric elements P in the piezoelectric-guided wave array is performed. i Structural lightning guided wave signal s i (t). Taking the impulse response guided wave signals s3(t) and s4(t) extracted from piezoelectric elements P3 and P4 as examples, the results are as follows: Figure 3 and Figure 4 The waveform shown.

[0071] (3) The lightning guided wave response signal is filtered by convolutional sinusoidal modulation signal:

[0072] The response signals of each lightning-struck guided wave are obtained by convolving a sinusoidal modulated signal. i (t) is filtered to obtain a narrowband lightning guided wave response signal with concentrated energy.

[0073] First, the lightning-guided wave response signals s of each structure were analyzed. i (t) Time-frequency domain analysis was performed to determine that the main guided wave mode in the signal is the A0 mode and the frequency range of the main energy distribution is 10kHz to 30kHz.

[0074] Based on the above analysis, choose as follows Figure 5 The shown signal is a three-peak sinusoidal modulated narrowband excitation signal v with a center frequency of 25kHz. a (t). v a (t) and the guided wave signals of each structural impact response s i (t) is convolved to obtain the structural narrowband shock waveguide signal v. i (t).

[0075] Taking the narrowband impulse guided wave signals v3(t) and v4(t) extracted by piezoelectric elements P3 and P4 as examples, respectively... Figure 6 and Figure 7 As shown in the waveforms, the direct waves in v3(t) and v4(t) are quite obvious.

[0076] (4) Determine the reference time of the lightning guided wave response signal based on crosstalk:

[0077] The position of each piezoelectric element P is determined by the crosstalk in the time domain. i Structural lightning guided wave signal s i(t) reference time t off .

[0078] And implement lightning strike integrated imaging based on signal delay superposition:

[0079] First, consider the various lightning-guided wave response signals s i (t) reference time t off Using the starting point of each signal, the guided wave response from point o to point P is calculated according to the following formula. i Propagation time t oi (x,y) is:

[0080]

[0081] Among them, (x i ,y i ) is a piezoelectric element P i The coordinates, c io For the guided wave response of a lightning strike to propagate from point O to P i wave speed;

[0082] Then, each lightning strike guided wave response signal s i (t) The magnitudes of the values ​​at point o are summed to calculate the pixel value of point o:

[0083]

[0084] Get as Figure 8 The comprehensive imaging results of the lightning source E1 shown are as follows: Figure 8 As can be seen, the pixel values ​​are higher and the imaging is more focused near the actual lightning strike point. Due to the anisotropic nature of the composite material plate, Figure 8 The actual lightning strike location deviated from the theoretical lightning strike location by approximately 12mm. However, this error is very small relative to the size of the entire board. Therefore, the imaging location is basically accurate, demonstrating the good imaging and monitoring capabilities of this imaging method, which can accurately locate the lightning strike point.

[0085] Therefore, the present invention adopts the above structure, firstly by using a sparse piezoelectric-guided wave array to expand the range of lightning strike monitoring of aerospace structures, and then by using the delay superposition of the lightning strike guided wave response signals of the piezoelectric array for comprehensive imaging. This not only realizes the online location monitoring of the lightning strike point, but also solves the problem of unknown pre-acquisition time and difficulty in imaging of traditional impact response signals.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A lightning strike imaging method based on piezoelectric array guided wave response, characterized in that: Includes the following steps: S1. Arrange a sparse piezoelectric-guided wave array in the structure under test; S2. Obtain the lightning-guided wave response signal of the sparse piezoelectric-guided wave array; S3. The lightning guided wave response signal is filtered by convolutional sinusoidal modulation signal; S4. Lightning guided wave response signal preprocessing and implementation of lightning strike comprehensive imaging based on signal delay superposition; The preprocessing of the lightning guided wave response signal in step S4 is as follows: determining each lightning guided wave response signal based on the crosstalk location. Reference time ; The implementation of lightning strike comprehensive imaging based on signal delay superposition in step S4 is as follows: using the response signals of each lightning guided wave... Reference time Using these signals as the starting points, and performing delayed superposition and comprehensive imaging processing, the comprehensive imaging results of the lightning strike are obtained.

2. The lightning strike imaging method based on piezoelectric array guided wave response according to claim 1, characterized in that: In step S1, arrangements are made on the structure under test. A sparse piezoelectric waveguide array is composed of several piezoelectric elements, in which .

3. The lightning strike imaging method based on piezoelectric array guided wave response according to claim 1, characterized in that: In step S2, when a lightning strike occurs, the individual piezoelectric elements in the sparse piezoelectric-guided wave array are passively acquired. Lightning-guided wave response signal ,in For time variables, .

4. The lightning strike imaging method based on piezoelectric array guided wave response according to claim 3, characterized in that: In step S3, the convolutional sinusoidal modulation signal is combined with the lightning-guided wave response signal. Convolution processing is performed to obtain a narrowband lightning guided wave response signal with more concentrated energy.

5. A lightning strike imaging method based on piezoelectric array guided wave response according to claim 4, characterized in that: Step S3 specifically includes the following steps: S31. Response signals of each lightning strike guided wave Perform low-pass filtering to remove high-frequency noise; S32. Analyze the individual lightning-guided wave response signals after filtering out high-frequency noise. Perform time-frequency domain analysis to determine the main guided wave modes in the signal, as well as the frequency range of the signal components and main distribution of these guided wave modes; The main waveguide mode is A0 mode, and the frequency range of the main energy distribution is 10kHz~30kHz. S33. Determine the narrowband excitation signal based on the frequency range determined in step S32. ; S34, will With the lightning strike guided wave response signals of each structure Convolution operations are performed to obtain the structural narrowband lightning-guided wave response signal. .

6. The lightning strike imaging method based on piezoelectric array guided wave response according to claim 1, characterized in that: Step S4, the delay-stack composite imaging processing, specifically includes the following steps: S41, using the response signals of each lightning strike guided wave Reference time As the starting point for each signal, the guided wave response to a lightning strike is calculated from point [point number] according to the following formula. to transmission time for: in, It is a piezoelectric element coordinates For the guided wave response of a lightning strike from point spread to wave speed; S42, convert each lightning strike guided wave response signal Corresponding points The amplitudes are superimposed to calculate the points. Pixel values: 。

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